Optimizing a prediction of resource usage of an application in a virtual environment

ABSTRACT

Described herein is a method for optimizing a prediction of resource usage of an application running in a virtual environment, comprising: providing a predetermined set of benchmarks, wherein the predetermined set of benchmarks; executing the predetermined set of benchmarks in a native hardware system in which the application natively resides; executing the predetermined set of benchmarks in the virtual environment; collecting first traces of first resource utilization metrics in the native hardware system based on the execution of the predetermined set of benchmarks in the native hardware system; collecting second traces of second resource utilization metrics in the virtual environment based on the execution of the predetermined set of benchmarks in the virtual environment; generating a first prediction model and a second prediction model; generating a third prediction model that maps all of the first traces of the selected first metric to the second traces of resource utilization metrics; comparing the first and second prediction models against the third prediction model; and predicting a resource usage of the application running in the virtual environment with either a) a combination of the first and second prediction models or b) the third prediction model based on the comparing.

CROSS-REFERENCE

This application is related to the following applications:

a) U.S. patent application Ser. No. 12/241,874, entitled, “PREDICTING RESOURCE USAGE OF AN APPLICATION IN A VIRTUAL ENVIRONMENT,” as filed on Sep. 30, 2008;

b) U.S. patent application Ser. No. 12/241,972, entitled, “DETECTING AN ERROR IN A PREDICTION OF RESOURCE USAGE OF AN APPLICATION IN A VIRTUAL ENVIRONMENT,” as filed on Sep. 30, 2008, now U.S. Pat. No. 7,818,145;

c) U.S. patent application Ser. No. 12/241,948, entitled, “SCALING A PREDICTION MODEL OF RESOURCE USAGE OF AN APPLICATION IN A VIRTUAL ENVIRONMENT,” as filed on Sep. 30, 2008;

d) U.S. patent application Ser. No. 12/241,913, entitled, “IMPROVING ACCURACY IN A PREDICTION OF RESOURCE USAGE OF AN APPLICATION IN A VIRTUAL ENVIRONMENT,” as filed on Sep. 30, 2008;

e) U.S. patent application Ser. No. 12/242,034, entitled, “OPTIMIZING A PREDICTION OF RESOURCE USAGE OF MULTIPLE APPLICATIONS IN A VIRTUAL ENVIRONMENT,” as filed on Sep. 30, 2008.

BACKGROUND

Virtualization and automation are key capabilities desired of Next Generation Data Centers (NGDC) for enterprises. As referred herein, a data center typically includes a location, such as a room that houses computer systems and associated components to store and manage data critical to the mission(s) of an enterprise. The primary motivation for enterprises to adopt virtualization technologies is the promise of creating a more agile and dynamic information technology (IT) infrastructure. To achieve this goal, virtualization technologies have been used to implement server consolidation so as to reduce the total number of servers in response to the problem of server sprawl in a data center. Server sprawl occurs when multiple, under-utilized servers take up more space and consume more resources than can be justified by their workloads.

One example of virtualization technologies being adopted for server consolidation is the Virtual Machine Monitor (VMM), also known as a Virtual Machine (VM) host or a hypervisor. The VMM is a software component or layer that is implemented in a physical or hardware machine, system, or platform to host VM guests therein, which are isolated virtual environments on the shared hardware platform. Accordingly, VMMs enable diverse applications to run in isolated environments on a shared hardware platform, and in such a way so as to provide some degree of fault and performance isolation between the consolidated applications.

As virtual machines and systems enter the mainstream and are deployed in larger numbers for implementation of NGDCs, manageability, automation, accurate resource accounting and quality-of-service-aware (QoS-aware) resource allocation have become the real differentiators to help enterprises create dynamic IT infrastructures for their NGDCs.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example and not limited in the following figure(s), in which like numerals indicate like elements, in which:

FIGS. 1A-B illustrate popular Input/Output (I/O) models of Xen® Virtual Machines.

FIG. 2 illustrates the goal of using native application traces to predict virtualized application traces, in accordance with one embodiment.

FIGS. 3A-B illustrate examples of the use of hardware platforms to implement native hardware system for an application and a virtual environment in which the application may be virtualized for execution, in accordance with one embodiment.

FIG. 4 illustrates a process for predicting resource usage of an application running in a virtual environment platform as it is transferred from its native hardware system, in accordance with one embodiment.

FIGS. 5A-B illustrate a comparison of errors for regression weighting functions, in accordance with one embodiment.

FIG. 6 illustrates another process for predicting resource usage of an application running in a virtual environment platform as it is transferred from its native hardware system, in accordance with one embodiment.

FIGS. 7A-B illustrates a process for optimizing a prediction of resource usage of an application running in a virtual environment platform, in accordance with one embodiment.

FIG. 8 illustrates a computerized system that may be used as platform to implement a native hardware system, a virtual system, and/or a client system, in accordance with one embodiment.

DETAILED DESCRIPTION

For simplicity and illustrative purposes, the principles of the embodiments are described by referring mainly to examples thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments. It will be apparent however, to one of ordinary skill in the art, that the embodiments may be practiced without limitation to these specific details. In other instances, well known methods and structures are not described in detail so as not to unnecessarily obscure the description of the embodiments.

A typical approach for evaluating which workloads can be efficiently consolidated together is based on multi-dimensional “bin packing” of resource usage traces. Typically, under such an approach, each application is characterized by its CPU, I/O and memory usage over time. Then a bin packing algorithm finds a combination of workloads with resource requirements which do not exceed the available server resources (some algorithms may allow a certain degree of resource overbooking as well as some additional constraints on workload placement). After the initial workload placement is done, additional workload management tools may be used to dynamically allocate system resources to match underlying application demands and to support the required application performance.

As described herein, various embodiments are concerned with the initial workload placement phase that receives as an input the application resource usage traces of its native hardware system or platform. It is important to know what an application's resource needs are going to be prior to transitioning it to a virtual environment with one or more virtual machines (VMs) therein. Resource requirements (in particular, CPU requirements) can increase due to virtualization overheads. If these overheads are not accounted for during initial planning, an application could be deployed to a server with insufficient resources, resulting in unacceptable application performance.

As illustrated in FIGS. 1A-B, there are two popular I/O models for VMs. These two VM models are demonstrated, for example, in the evolution of the I/O architecture of Xen®, which is an open-source VMM or hypervisor that serves as an abstraction layer between the physical hardware 180 and one or more VM guests 120 (hereinafter, “VM 120”). In its original design, as illustrated in FIG. 1A, the Xen hypervisor 110 itself contained device driver code, as illustrated by the network driver 112 and disk driver 114, and provided safe, shared access for I/O hardware, as illustrated by the Network Interface Card or Controller (NIC) 116 and the disk drive 118, for the VM guest 120. In its current design, as illustrated in FIG. 1B, the Xen hypervisor 110 no longer hosts device driver code. Instead, unmodified device drivers, such as the network driver 112 and disk driver 114, are allowed to be hosted and executed in one or more isolated “driver domains,” as illustrated by a management Domain-0 130 (hereinafter, “dom-0 130”). Typically, the dom-0 130 hosts unmodified device drivers, such as Linux® device drivers, and plays the role of the driver domain. Thus, the current I/O model in FIG. 1B results in a more complex CPU usage model. That is, for I/O intensive applications, CPU usage has two components: CPU consumed by the VM guest 120 and CPU consumed by the dom-0 130 which hosts the device drivers 112, 114 and performs I/O processing on behalf of the guest domain 120. Note that a trace is an ordered series, such as a time series, of monitored or collected data on performance metrics (for example, resource usage metrics of an application) of a system such as a server. Application resource usage traces are routinely collected over some time period (e.g., 3-6 months) to get a representative application resource usage profile. Then these traces can be used for capacity planning and workload placement or for other uses.

Accordingly, various embodiments as described herein provide a methodical approach for predicting the CPU requirements of applications (or workloads) when they are transferred to a virtual environment. That is, given resource utilization traces of an application running natively on its hardware system or platform, the various embodiments aim to predict what the application's resource requirements would be if it were transitioned to a virtual environment on a given hardware platform. For example, a collection of application resource usage traces (over time) in a native hardware system or platform is monitored and provided as shown in FIG. 2 at the top to show CPU utilization 210, transferred and received networking packets 212, and read and write bytes (disk) 214. The goal is to use these native application resource usage traces to predict virtualized application traces, or resource needs in a virtual environment to run the same application. Namely, as shown in FIG. 2 at the bottom, the predicted resource needs are the CPU requirement 220 of the VM guest domain 120 where the application is going to reside and execute and the CPU requirement 222 of the dom-0 130 which performs I/O processing on behalf of the VM guest domain 120 to facilitate the execution of the application within the later.

As described herein, it is expected that the CPU utilization of the VM guest 120 is highly correlated and proportional to the native CPU usage profile of the application, while the CPU utilization of the dom-0 130 is mostly determined by a combination of I/O profiles (both network and disk). As also described herein, there is a focus on predicting CPU utilization in the virtualization system because other performance metrics, such as disk and network request rates, are not directly impacted by the virtualization layer. As used herein, “disk” or “disk memory” refers to the main storage mechanism used to store data as opposed to cache memory such as Random Access Memory (RAM) chips in a hardware system. Disk memory may include, for example, a hard disk drive and/or a removable storage drive representing a floppy diskette drive, a magnetic tape drive, a compact disk drive, etc., or a nonvolatile memory where a copy of the software is stored. Disk memory may also include, for example, ROM (read only memory), EPROM (erasable, programmable ROM), EEPROM (electrically erasable, programmable ROM), or any other electronic, optical, magnetic, or other storage or transmission device capable of electronic data storage.

In one embodiment, the prediction of CPU requirements of virtualized applications (that is, applications running in a virtual environment or system) includes the following components: a) a benchmark suite having a predetermined set of benchmarks to profile the different types of virtualization overhead on a given hardware platform, whereby the benchmark suite is executed on the native hardware and in a virtual environment to create a “native” resource usage profiles and a “virtual” resource usage profiles; and b) regression-based computation to create a model that maps the “native” hardware system usage profile into the “virtual” one, whereby this model helps to predict the resource requirements of any application to be virtualized on a given hardware platform.

Accordingly, the benchmark suite is first used to accumulate samples of resource usage profiles by executing the benchmark suite in both native and virtual environments so as to collect benchmark data for different benchmark sets to determine a general relationship between the application resource usage in native and virtual systems. Then a model may be created for the virtual environment or system, which is hosted or implemented on the same or different hardware system as the native hardware system, to predict resource requirements for the virtualized application. For example, FIG. 3A illustrates the use of a native system resource usage profile 310 and a virtual system resource usage profile 320 running on separate hardware systems or platforms #1 and #2 to generate or create a first model 350 for predicting resource requirements of a virtualized application. However, the hardware systems #1 and #2 have substantially identical system configurations, such as both hardware systems #1 and #2 are AMD® Opteron™ systems. Thus, the hardware systems #1 and #2 may be one and the same. In another example, FIG. 3B illustrates the use of a native system resource usage profile 310 running on separate hardware systems (or platforms) #1 and #3 to generate or create a second different model 360 for predicting resource requirements of a virtualized application. However, the hardware systems #1 and #3 have different system configurations, such as the hardware system #1 may be an AMD® Opteron™ system and the hardware system #3 may be an Intel® Xeon™ system. The benchmark suite and prediction modeling are further detailed below.

At a high level, the benchmark suite includes three types or patterns of workload that cause a test system (hardware or virtual) to perform CPU-intensive computation, send and receive network packets, and read and write to disk. A client system may be used to provide inputs to the test system so as to adjust the rate and type of requests to control the amount (intensity) of CPU computation and I/O activities performed on the test system. The same client system also may be used to generate the prediction model for resource usage of a virtualized application.

As referred herein, a CPU-intensive workload predominantly takes up the computational resources, such as CPU resources, of a test system during its execution in the test system while remaining minimally taxing to other resources, such as networking and memory I/O resources, of the test system. For example, the CPU-intensive computation workload calculates the Fibonacci series when it receives a request from, for example, a client system. The number of terms in such a series may be varied to adjust the load and computation time on the test system. It should be understood that other mathematical algorithms or known computational intensive algorithms may be used in lieu of the Fibonacci series for the CPU-intensive computation workload.

Similarly, as referred herein, a network-intensive workload predominantly takes up the networking resources of the test system during its execution in the test system while remaining minimally taxing to other resources of the test system. In one embodiment, the network-intensive workload has two modes depending on the type of client request. In transmit mode, each incoming client request results in a large file being sent from the system being tested to the client system. In receive mode, one or more clients upload files to the benchmark application. The size of transferred files and the rate of client requests may be varied to adjust the network utilization rate.

Likewise, as referred herein, a disk- or memory-intensive workload predominantly takes up the memory I/O resources of the test system during its execution in the test system while remaining minimally taxing to other resources of the test system. In one embodiment, the disk-intensive workload has read and write modes. In these two modes, a random file is either, respectively, read from or written to a multi-level directory structure. File size and request rate may be adjusted to control the disk I/O rate.

Accordingly, each workload is created by adjusting the request type sent to the test system from a client system or machine. In one embodiment, each type of CPU-, network-, and disk-intensive workload patterns is further divided into several (for example, five) different intensities ranging from 10% load to 90% maximum load on the test system. The maximum load that a test system can handle is determined by increasing the throughput of benchmark requests from the client until either the CPU of the VM 120 or dom-0 130 becomes saturated during testing. The range of intensities are then measured for each workload type in order to build an accurate prediction model for the full working range of the virtual server. In one embodiment, the benchmark suite may be implemented as a set of Hypertext Preprocessor (PHP) scripts running on a web server at the bench-marked server side. Thus, the benchmark suite may be easily deployed and executed as software applications on a wide range of hardware systems or platforms within a software environment that is already familiar with data center administrators. Consequently, the developed benchmark suite is operable to generate a diverse set of simple and more complex workloads that exercise different components of a test system.

While the benchmark suite is running or executing on each test system, namely, the native hardware system and the virtual system, resource utilization traces of each system are gathered or collected, for example, by an automated benchmark system, to define the platform profiles used as the training set or data for the prediction model. In one embodiment, within the native hardware system, resource utilization traces of eleven different resource metrics or measurements related to CPU utilization, network activity, and disk I/O are gathered or collected. A list of these resource metrics is shown in Table 1. Within the virtual system based on the current I/O model illustrated in FIG. 1B, resource utilization traces of two CPU utilization metrics for the VM 120 and dom-0 130 are also collected or gathered. Alternatively, if the original I/O model of VM as illustrated in FIG. 1A is employed, resource utilization traces of two CPU utilization metrics for the VM 120 and hypervisor 110 are collected or gathered. These resource utilization traces are to be gathered or collected with low overhead. Furthermore, because these traces are to be gathered from a live application being transitioned to a virtual environment, a lightweight monitoring system may be used to gather data. For example, they may be gathered in Linux™ with the Sysstat monitoring package.

TABLE 1 CPU Utilization Network Utilization Disk Utilization User Space % Rx packets/sec Read requests/sec Kernel % Tx packets/sec Write requests/sec I/O Wait % Rx bytes/sec Read blocks/sec Tx bytes/sec Write blocks/sec

The time and workload type of each resource utilization trace are stored to simplify data processing and allow for the possibility of targeted benchmark reruns. As shown in Table 1, three CPU-related metrics are monitored, namely, the user space % CPU utilization, the kernel space % CPU utilization, and the I/O wait % CPU utilization, because different types of activities may have different virtualization overheads. For example, user space processing such as simple arithmetic operations performed by an application are unlikely to have much overhead in current virtualization platforms. In contrast, tasks which occur in the kernel space, such as context switches, memory management, and I/O processing, are likely to have a higher level of overhead because they may use traps to the hypervisor. User space % CPU utilization refers to the percentage (%) of CPU resources used to run the user space (defined by an operating system that manages the native hardware system) and any application executing therein, kernel space % CPU utilization refers to the percentage of CPU resources used to run the kernel space (also defined by the operating system that manages the native hardware system), and I/O wait % CPU utilization refers to the percentage of CPU resources that are tied up while an application is waiting for I/O operations such as read and write.

For network utilization, both the packet rates and byte rates of the network interfaces are measured or monitored because different virtual environments may handle I/O virtualization in different ways. For example, prior to Xen version 3.0.3, incoming network packets were passed between the dom-0 130 and the VM guest domain 120 by flipping ownership of memory pages. Thus, the CPU overhead associated with receiving each packet was independent of the packet's size. Newer versions of Xen directly copy packets from the dom-0 130 to the VM guest domain 120 rather than using page flipping. Thus, the overhead is also related to the number of bytes received per second, not just the number of packets. The paths for sending and receiving are differentiated because they may have different optimizations. For disk (or memory) utilization, disk measurements are divided into four categories based on similar reasoning as also shown in Table 1.

Table 2 shows a sample of platform profile of collected resource usage traces of the executed benchmark suite. The first column indicates the time intervals at which the traces are collected. The second column provides an identification of the particular benchmark set in the benchmark suite, which is executed to generate the associated resource utilization traces that form the benchmark data for the particular benchmark set, so that the same benchmark set may be used for a rerun as desired in the future. For example, a benchmark suite may include multiple benchmark sets, with each set created from one or more workload types and different workload parameters therein, such as different I/0 rates, load intensities, etc. The next eleven columns indicate benchmark data collected on the native hardware system for each of the eleven selected resource utilization metrics noted above. The last two columns indicate data collected for CPU utilizations of the VM guest domain 120 and the dom-0 130 in the virtual environment, as also noted above for the current I/O model of VM illustrated in FIG. 1B. Again, alternatively, if the original I/O model of VM as illustrated in FIG. 1A is employed by the native system, the last two columns are used to indicate data collected for CPU utilizations of the VM guest domain 120 and hypervisor 110 as percentages of total CPU resources available in the virtual system.

TABLE 2 Bench- User . . . CPU CPU Time mark CPU Rx . . . Rd Write VM D-0 Int. ID % . . . Pkts/s . . . Blks/s Blks/s % % 1 1 22 . . . 500 . . . 80 120 24 8 2 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Using a regression-based approach, a prediction model is generated or created to map the native hardware system usage profile into a virtual one. This model helps to predict the resource requirements of any application to be virtualized on a given hardware platform. Thus, to find the relationship between the application resource usage in native and virtual systems, the collected resource usage platform profile, such as the one shown in Table 2, is used to form a set of equations that calculate CPU utilization of the dom-0 130 as a linear combination of the different metrics: U _(dom0) ¹ =c ₀ +c ₁ *M ₁ ¹ +c ₂ *M ₂ ¹ + . . . +c ₁₁ *M ₁₁ ¹ U _(dom0) ² =c ₀ +c ₁ *M ₁ ² +c ₂ *M ₂ ² + . . . +c ₁₁ *M ₁₁ ²  (1) where M_(j) ^(i) is a value of metric M_(i) collected during the time interval j for a benchmark set executed in the native environment, and U_(dom0) ^(j) is a measured CPU utilization for a benchmark set executed in the virtual environment (for example, domain-0 130) with the corresponding time interval j.

With c₀ ^(dom0), c₁ ^(dom0), . . . , c₁₁ ^(dom0) denoting the approximated solution for the equation set (1), an approximated utilization Û_(dom0) ^(j) is calculated as:

$\begin{matrix} {{\overset{\Cap}{U}}_{{dom}\; 0}^{j} = {c_{0}^{{dom}\; 0} + {\sum\limits_{i = 1}^{11}{M_{i}^{j} \cdot c_{i}^{{dom}\; 0}}}}} & (2) \end{matrix}$ To solve for c_(i) ^(dom0) (0≦i≦11), any regression method may be used. For example, the least squares regression method may be used to solve the set of equations (1) and (2) so as to calculate the c₀ ^(dom0), c₁ ^(dom0), . . . , c₁₁ ^(dom0) coefficients while minimizing the error:

$\begin{matrix} {e = \sqrt{\sum\limits_{j}\left( {{\overset{\Cap}{U}}_{{dom}\; 0}^{j} - U_{{dom}\; 0}^{j}} \right)_{j}^{2}}} & (3) \end{matrix}$

The set of coefficients c₀ ^(dom0), c₁ ^(dom0), . . . , c₁₁ ^(dom0) is a first prediction model that describes the relationship between the application resource usage in the native system and application CPU usage in the dom-0 130. Another set of equations similar to the set of equations (1) are also formed to characterize the CPU utilization of the VM guest domain 120 by replacing U_(dom0) ^(i) with U_(cm) ^(i). The resulting solution c₀ ^(vm), c₁ ^(vm), . . . , c_(n) ^(vm) then defines a second prediction model that relates the application resource usage in the native system and application CPU usage in the VM 120 running the application. Thus, with known values of M_(j) ^(i) for metrics M_(i) at time intervals j for an application running in the native system and known sets of coefficients c₀ ^(dom0), c₁ ^(dom0), . . . , c₁₁ ^(dom0) and c₀ ^(vm), c₁ ^(vm), . . . , c_(n) ^(vm), the sets of equations (2) for both U_(dom0) ^(i) and U_(vm) ^(i) may be used to effectively predict the resource usage of the same application when virtualized in a particular virtual system.

Accordingly, FIG. 4 illustrates a method 400 for predicting resource usage, particularly, CPU requirements, of an application running in a virtual environment or system as it is transferred from its native hardware system, in accordance with one embodiment. For illustrative purposes only and not to be limiting thereof, FIG. 4 is discussed with reference to the VM model illustrated in FIG. 1B and systems illustrated in FIGS. 3A-B.

At 410, a benchmark suite is prepared or provided to include a plurality of benchmark sets of benchmarks of CPU-intensive computation, network-intensive, and disk-intensive workloads as described earlier.

At 412, the benchmark suite is executed in a native hardware system so as to gather resource utilization traces of such a system as it executes the benchmark suite. The native hardware system is, for example, the hardware system #1 in FIGS. 3A-B that is initially used to natively run a desired application which is now desired to be run in a desired virtual environment or system within the same hardware system #1 (FIG. 3A) or in a different hardware system #2 (FIG. 3B).

At 414, the resource utilization traces of the native hardware system (that is, the traces of the eleven resource utilization metrics in the native hardware system) are collected to form a native hardware system profile while the benchmark suite is running therein.

At 416, the benchmark suite is also executed in the desired or selected virtual environment that is to replace the native hardware system for running the desired application.

At 418, the resource utilization traces of the virtual system (that is, the traces of the two CPU utilization metrics in the virtual system) are also collected to form a virtual system profile while the benchmark suite is running in the virtual system.

At 420, as described earlier, one or more prediction models are generated using a regression-based approach to map the native hardware system profile to the virtual system profile.

At 422, the prediction model(s) may be used to predict a resource usage of an application running in the virtual system once it migrates over from the hardware system in which it natively resides and runs. That is, once a prediction model is generated or created, it may be applied to resource utilization traces of other applications in order to predict what their CPU requirements are going to be once they are transferred to a virtual environment.

The method 400 as illustrated in FIG. 4 is also applicable for generating prediction models for the hypervisor 110 and VM 1200 for a virtual environment that follows the VM model illustrated in FIG. 1A.

As described above, both the native hardware and virtual systems run an identical benchmark suite. The resource utilization traces from both systems are then gathered, for example, by an automated benchmark system, to define the platform profiles that are used as training data for the prediction model. There are instances where errors, such as benchmark timing errors, and noises, such as those generated by anomalous background processes can skew the measurements, leading to incorrect data points in the platform profiles. There is a possibility that a few incorrect data points, or bad outliers, may significantly impact the model accuracy as achieved by the aforementioned regular least squares regression method, which is based on minimizing the overall absolute error across multiple equations in a set of data points. That is, the regular least squares regression method generates a prediction model by creating an initial linear regression fit for a set of data points and then refining that fit based on the error between each data point and the initial linear regression line. Data points pull the line towards them based on their weight, which is equal to the square of the distance from each data point to the line. Thus, the weight of a data point increases quadratically with its error as shown in FIG. 5A. This can lead to a few bad data points, such as bad outliers, having more sway or effect over the linear regression line than they should.

Accordingly, in one embodiment, to lessen the impact of occasional bad measurements, a more robust linear regression method, such as the iteratively reweighted least squares regression method, is employed in lieu of the aforementioned regular least squares regression method. This robust linear regression method uses a weighted least squares algorithm, such as a bisquare weighting function which is initially quadratic, but then levels off to lessen the weight of outliers, or data points with high error, as illustrated in FIG. 5B.

A direct or naïve linear regression approach, such as the least squares regression method described above, operates to set non-zero values to all the model coefficients (c₀ ^(dom0), c₁ ^(dom0), . . . , c₁₁ ^(dom0) and c₀ ^(vm), c₁ ^(vm), . . . , c_(n) ^(vm)) in order to produce the minimal error, e, when the prediction model is applied to the training set (or platform profiles). Thus, the prediction model is finely tuned to the training set. To further improve prediction accuracy when the prediction model is later applied to data sets other than the training set that correlate with the actual CPU utilization, statistically significant metrics from the list of metrics M_(i) are chosen or selected for actual use by the prediction model. In one embodiment, a stepwise linear regression method is used to determine which set of input metrics are the best predictors for the output variable of the prediction model.

FIG. 6 illustrates a method 600 that uses a stepwise linear regression approach to further improve the prediction model(s) as generated at 420 in FIG. 4. For illustrative purposes only and not to be limiting thereof, FIG. 6 is discussed with reference to the VM model illustrated In FIG. 1B and systems illustrated in FIGS. 3A-B.

At 610, an “empty” prediction model is initialized, wherein the prediction model includes none of the possible performance metrics collected from the native system, such as the eleven performance metrics listed in Table 1.

At 612, a computational iteration is initiated to select a new metric for inclusion in the prediction model. That is, for each metric M_(i) (1≦i≦11), the following set of equations are formed to calculate CPU utilization of the dom-0 130 based on the monitored particular metric M_(i): U _(dom0) ¹ =c ₀ +c _(i) *M _(i) ¹ U _(dom0) ² =c ₀ +c _(i) *M _(i) ²  (4)

With c₀ ^(dom0), c_(i) ^(dom0) denoting the approximated solution for the equation set (4) for each particular metric M_(i), an approximated utilization Û_(dom0) ^(j) for the same metric is calculated as: Û _(dom0) ^(j) =c ₀ ^(dom0) +M _(i) ^(j) ·c _(i) ^(dom0)  (5) To solve for c₀ ^(dom0) and c_(i) ^(dom0) for each particular metric M_(i), any regression method may be used, with c₀ ^(dom0) playing the role of a static offset. For example, the least squares regression method as described earlier may be used to solve the set of equations (4) and (5) so as to minimize the error:

$\begin{matrix} {e_{i} = \sqrt{\sum\limits_{j}\left( {{\overset{\Cap}{U}}_{{dom}\; 0}^{j} - U_{{dom}\; 0}^{j}} \right)_{j}^{2}}} & (6) \end{matrix}$ which is similar to equation (3) above. Alternatively, a more robust linear regression technique, such as the iteratively reweighted least squares method that uses a bisquare weighting function may be used to lessen the impact of outliers. The best metric M_(i) is chosen by adding the metric which results in the lowest mean squared error when it is included. That is M_(k) (1≦k≦11) is selected such that,

$\begin{matrix} {e_{k} = {\min\limits_{1 < i < 11}e_{i}}} & (7) \end{matrix}$

At 614, before the selected metric M_(k) is added to the prediction model, a determination is made as to whether the inclusion of such a selected metric results in a statistically significant improvement in the accuracy of the prediction model. Thus, in one embodiment, a statistical test, such as an F-test, is performed on the prediction model with the selected metric M_(k) included therein.

At 616, If the F-test fails, the stepwise regression method 500 is terminated because additional metrics do not provide a significant benefit. Thus, the coefficient c_(k) ^(dom0) corresponding to the selected metric M_(k) and other metrics M_(i) that are not to be included in the prediction model are set to zero so as to exclude such metrics from the prediction model.

At 618, however, if the F-test passes, the selected metric M_(k) is added to the prediction model, and the next iterative is repeated at 512 to choose the next metric from the remaining subset of metrics.

A similar method to the method 600 is applied to generate a prediction model to predict CPU requirements by the VM 120.

Again, the method 600 as illustrated in FIG. 6 is also applicable for generating prediction models for the hypervisor 110 and VM 1200 for a virtual environment that follows the VM model illustrated in FIG. 1A.

There are examples where additional system optimizations may be introduced under high system loads to optimize the overall performance of a system, native or virtualized. These system optimizations are typically applied to, for example, network scheduling for network utilization and/or disk scheduling for disk utilization. Such system optimizations facilitate the implementation of a non-linear prediction modeling scheme, wherein a system behavior and its resource consumption may be described by one prediction model when the system or resource utilization is below a predetermined system utilization level or threshold and by a different prediction model when the resource utilization is above this threshold.

In one example, with the scheduling of disk read/write requests, when disk requests arrive at a low rate, each is serviced individually with certain latency and disk utilization. Thus, one would expect that, for example, a five-fold increase in the arrival rate of disk requests would linearly correspond to a five-fold increase in the disk utilization. However, there is typically scheduling optimization for a high rate of disk requests, wherein instead of servicing each disk request separately, the requests in a queue are reordered in such a way that all of them are serviced during one disk rotation. Thus, two different “resource usage” or prediction models may be defined based on different arrival rates of disk requests. It should be noted that there are other examples of “grouping” operations that result in a similarly improved prediction model under heavier system loads.

Accordingly, to ensure that the aforementioned additional system optimizations are taken into consideration in the prediction models, additional model optimization is performed, as provided by the method 700, which is illustrated in FIGS. 7A-B, in accordance with one embodiment. For illustrative purposes only and not to be limiting thereof, FIGS. 7A-B are discussed with reference to the VM model illustrated in FIG. 1B and systems illustrated in FIGS. 3A-B. Furthermore, although the method 700 is discussed with reference to disk I/O requests (e.g., read/write requests), it should be understood such a method is applicable for other examples of “grouping” operations (or resource utilization traces) that result in a similarly improved resource utilization model under heavier loads. Method 700 commence once the benchmark suite is run or executed on each test system, namely, the native hardware system and the virtual system, resource utilization traces of each system are gathered or collected (see 410-418 in FIG. 4).

At 710, the monitored time intervals of one or more resource utilization traces of interest (see M_(j) ^(i) in equation (1)) are ordered based on rate information, such as ist monitored rate. For example, the monitored time intervals for disk read requests are ordered as R₁, . . . , R_(m) where m is the highest rate of read requests/sec. Rate information describes the intensity that a benchmark is executed. As an example, rate information may be a percentage of full capacity, such as 0-40% of maximum number of requests per second for the environment. The same rate information is used to determine traces in both the native and virtual environments.

At 712, a value k is iteratively selected from the following desired range 2≦k≦m−1.

At 714, through the iterative process that begins at 712, two prediction models with complementary data sets (monitored time intervals) are generated or built. First, a first prediction model model₁ built based on the monitored time intervals for disk read requests/sec where the data rate is less than or equal to a predetermined data rate, or R₁≦R_(k). The model₁ represents a prediction model under lighter loads and is generated in a manner as described earlier with reference to equations (1)-(3). The aforementioned robust linear regression and/or stepwise linear regression may be implemented here as well.

At 716, a second prediction model model₂ is built based on the monitored time intervals for disk read requests/sec where R_(k+1)≦R_(m). The model₂ represents a prediction model under heavier loads and is generated in a manner as described earlier with reference to equations (1)-(3). Again, the aforementioned robust linear regression and/or stepwise linear regression techniques may be implemented here as well.

At 718, the error e₁ is calculated for the model₁ and the error e₂ is calculated for the model₂ using, for example, equation (3) for robust linear regression or equation (7) for stepwise regression as described earlier.

At 720, a prediction model model₀ which represents an overall or “single-segment” solution is also generated or built using the overall data set of monitored time intervals (see 420 in FIG. 4).

At 722, the error e₀ is also calculated for the model₀, using equation (3) or (7) as noted above.

At 724, a comparison is made to determine whether the combined error e₁+e₂ of the two models is smaller than the error e₀ of the single-segment model model₀.

At 726, if the combined error e₁+e₂ is smaller than e₀, then the two-segments model defined by model₁ and model₂ are used to represent the application resource scaling rules at different I/O rates of the modeled application. That is, different scaling prediction models are used (e.g., at 422 in FIG. 4) for predicting CPU overhead of the application in a virtual environment where the choice of which model to apply depends on the I/O rates of the underlying application.

At 728, if the combined error e₁+e₂ is larger than e₀, then the single-segment model models is used (e.g., at 422 in FIG. 4).

FIG. 8 illustrates a block diagram of a computerized system 800 that is operable to be used as a platform for implementing a client system that may be used to provide inputs to the test native hardware and virtual systems to generate the prediction model as described earlier. Another computerized system 800 may also serve as a native hardware system and/or a hardware platform on which a virtual system is implemented.

The computer system 800 includes one or more processors, such as processor 802, providing an execution platform for executing software. Thus, the computerized system 800 includes one or more single-core or multi-core processors of any of a number of computer processors, such as processors from Intel, AMD, and Cyrix. As referred herein, a computer processor may be a general-purpose processor, such as a central processing unit (CPU) or any other multi-purpose processor or microprocessor. A computer processor also may be a special-purpose processor, such as a graphics processing unit (GPU), an audio processor, a digital signal processor, or another processor dedicated for one or more processing purposes. Commands and data from the processor 802 are communicated over a communication bus 804 or through point-to-point links with other components in the computer system 800.

The computer system 800 also includes a main memory 806 where software is resident during runtime, and a secondary memory 808. The secondary memory 808 may also be a computer-readable medium (CRM) that may be used to store software programs, applications, or modules that implement the methods or processes in FIGS. 4-7, applications running natively, and/or components for a virtual environment (such as a hypervisor, driver domains, and VM guests). The main memory 806 and secondary memory 808 (and an optional removable storage unit 814) each includes, for example, a hard disk drive 810 and/or a removable storage drive 812 representing a floppy diskette drive, a magnetic tape drive, a compact disk drive, etc., or a nonvolatile memory where a copy of the software is stored. In one example, the secondary memory 808 also includes ROM (read only memory), EPROM (erasable, programmable ROM), EEPROM (electrically erasable, programmable ROM), or any other electronic, optical, magnetic, or other storage or transmission device capable of providing a processor or processing unit with computer-readable instructions. The computer system 800 includes a display 820 connected via a display adapter 822, user interfaces comprising one or more input devices 818, such as a keyboard, a mouse, a stylus, and the like. However, the input devices 818 and the display 820 are optional. A network interface 830 is provided for communicating with other computer systems via a network, such as the Internet or an intranet. For example, if the computerized system 800 is used to implement the client system, the network interface 830 may be used to provide inputs to the test systems via a network and receive resource usage traces from the test systems. If the computerized system 800 is used as a hardware platform for the native hardware or virtual systems, the network interface 830 may be used to communicate with the client system to receive inputs for running the benchmark suite and provide resulting resource usage traces to the client system.

What has been described and illustrated herein is an embodiment along with some of its variations. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the subject matter, which is intended to be defined by the following claims—and their equivalents—in which all terms are meant in their broadest reasonable sense unless otherwise indicated. 

1. A method for optimizing a prediction of resource usage of an application running in a virtual environment, comprising: providing a predetermined set of benchmarks; executing the predetermined set of benchmarks in a native hardware system in which the application natively resides; executing the predetermined set of benchmarks in the virtual environment; collecting first traces of first resource utilization metrics in the native hardware system based on the execution of the predetermined set of benchmarks in the native hardware system; collecting second traces of second resource utilization metrics in the virtual environment based on the execution of the predetermined set of benchmarks in the virtual environment; generating a first prediction model that maps a first selected set of the first traces of the selected first metric to the second traces of resource utilization metrics; generating a second prediction model that maps a second selected set of the first traces of the selected first metric to the second traces of resource utilization metrics; generating a third prediction model that maps the first and second selected sets of the first traces of the selected first metric to the second traces of resource utilization metrics; comparing the first and second prediction models against the third prediction model; and predicting a resource usage of the application running in the virtual environment with either a) a combination of the first and second prediction models or b) the third prediction model based on the comparing.
 2. The method of claim 1, further comprising: ordering the first traces of a selected first metric of the first resource utilization metrics based on rate information in the traces.
 3. The method of claim 2, wherein the selected first metric is an Input/Output metric for a memory access, and the rate information is an I/O rate of the memory access.
 4. The method of claim 2, further comprising: identifying the first selected set of the first traces of the selected first metric based on the ordering of the first traces in a first selected range of the rate information in the traces; identifying the second selected set of the first traces of the selected first metric based on the ordering of the second traces in a second different selected range of the rate information in the traces.
 5. The method of claim 1, further comprising: calculating a first error associated with the first prediction model; calculating a second error associated with the second prediction model; and calculating a third error associated with the third prediction model.
 6. The method of claim 5, wherein comparing the first and second prediction models against the third prediction model comprises: comparing a combined error of the first and second errors against the third error.
 7. The method of claim 6, wherein: upon determining that the combined error is less than the third error, predicting the resource usage of the application running in the virtual environment with the combination of the first and second prediction models.
 8. The method of claim 6, wherein: upon determining that the combined error is greater than or equal to the third error, predicting the resource usage of the application running in the virtual environment with the third prediction error.
 9. The method of claim 1, further comprising: performing a linear regression computation for generating at least one of the first, second, and third prediction models.
 10. The method of claim 9, wherein performing the linear regression computation comprises: performing a robust linear regression computation for generating at least one of the first, second, and third prediction models.
 11. The method of claim 9, wherein performing the linear regression computation comprises: performing a stepwise linear regression computation for generating at least one of the first, second, and third prediction models.
 12. A system for optimizing a prediction of resource usage of an application running in a virtual environment, comprising: a first hardware platform implementing a native hardware system in which an application natively resides and executes, the native hardware system operating to execute a predetermined set of benchmarks; a second hardware platform implementing a virtual environment therein, the virtual environment operating to execute the predetermined set of benchmarks; a third hardware platform operating to collect first resource usage traces from the first hardware platform that result from the execution of the predetermined set of benchmarks in the native hardware system and second resource usage traces from the second hardware platform that result from the execution of the predetermined set of benchmarks in the virtual environment; wherein the third hardware platform further operates to generate a first prediction model, a second prediction model, and a third prediction model that predict a resource usage of the application executing in the virtual environment with either a combination of the first and second prediction models or based on a comparison of the first and second prediction models against the third prediction model.
 13. The system of claim 12, wherein the third hardware system further operating to calculating a first error associated with the first prediction model, a second error associated with the second prediction model, and a third error associated with the prediction model.
 14. The system of claim 13, wherein the third hardware system further operating to compare a combined error of the first and second errors against the third error so as to predict a resource usage of the application executing in the virtual environment.
 15. A computer readable medium on which is encoded programming code executed by a computer processor to optimize in a prediction of resource usage of an application running in a virtual environment, the encoded programming code comprises: programming code for providing a predetermined set of benchmarks, wherein the predetermined set of benchmarks; programming code for executing the predetermined set of benchmarks in a native hardware system in which the application natively resides; programming code for executing the predetermined set of benchmarks in the virtual environment; programming code for collecting first traces of first resource utilization metrics in the native hardware system based on the execution of the predetermined set of benchmarks in the native hardware system; programming code for collecting second traces of second resource utilization metrics in the virtual environment based on the execution of the predetermined set of benchmarks in the virtual environment; programming code for generating a first prediction model that maps a first selected set of the first traces of the selected first metric to the second traces of resource utilization metrics; programming code for generating a second prediction model that maps a second selected set of the first traces of the selected first metric to the second traces of resource utilization metrics; programming code for generating a third prediction model that maps the first and second selected sets of the first traces of the selected first metric to the second traces of resource utilization metrics; programming code for comparing the first and second prediction models against the third prediction model; and programming code for predicting a resource usage of the application running in the virtual environment with either a) a combination of the first and second prediction models or b) the third prediction model based on the comparing. 